Olivier Marty and Karl Fournier met nineteen years ago as architecture students studying at Paris’s École des Beaux-Arts. Marty was the keen-eyed pragmatist, Fournier, who had initially trained to be an actor, the conceptually minded dreamer. The combination was apparently electric: A week later, Fournier had bought Marty a ticket to his homeland of Corsica, where they spent a winter holiday, exploring the island via roads that snake through terrifying hairpin bends with plunging chasms below. “I wasn’t a southern guy at all,” says Parisian-born Marty. “All of my family would go to Brittany on holiday.” But Corsica’s beautiful, tough landscape, with its mountainous inland smothered in dense and impenetrable maquis vegetation, and its coastline of cliffs and rocks, cast a spell. “I have a very strong memory of that February light,” says Marty, “of the nature, the smell of wood burning in the wintertime. Since then I’ve felt very at home here.”

It was to this remembered paradise that Marty and Fournier returned fifteen years later when they decided to buy a holiday house on the island, a challenging proposition as properties rarely appear on the open market. They were struck by a village in the far north, with a café in the square and a bell tower that not only peals for the three local churches but also serves as a lighthouse—and an Addams Family castle on a cliff (one of the maisons Américaines built at the turn of the century by returning adventurers keen to flaunt the wealth acquired in the brave new worlds). The two acquired a nineteenth-century village house on a street where the local carpenters traditionally had their workshops. The elderly Italian lady who had filled it with Madonna statues and antimacassars had died some years before, and the house was abandoned and desolate, its sad backyard choked with weeds, rubble, and a burned-out car carcass.

“We liked that it was not a shepherd’s house,” says Marty. “It has real rooms that have a very noble shape and proportion, but it’s very poor. It has no ornament, nothing formal.”

Working with skilled local craftspeople, the couple restored the structure with a sensitivity to its history, using the region’s characteristic rough-edged slate tiles for the roof, and carefully copying the dimensions of a neighbor’s original chimneypiece to replace a later addition. They even instructed their painters to leave small unpainted “windows” to reveal the original nineteenth-century wall colors in a brace of guest rooms, a playful homage to a similar effect they had seen when they stayed at the Villa Medici in Rome. The house also reflects their keen eye for deft and unobtrusive contemporary interventions. “We wanted it to be very fresh, light, and clean,” says Marty, so they painted the hexagonal terra-cotta tommette tiles on the second floor a pale gray, and selected vast glazed windows to replace the solid stable doors on the ground floor. Meanwhile, their friend the landscape architect Arnaud Casaus fashioned a pocket Eden in the former junkyard, now a garden of darting lizards, planted in a harmony of soft mauve-blues with agapanthus, Thunbergia, Vitex agnus-castus, plumbago, and morning glory. On balmy days meals of such local delicacies as a filetta, a potent, dense cheese; wild-boar saucisson; cedrat and bramble jams; and chestnut cake are served alfresco, on a raised terrace crowned with a canopy covered in split reeds, inspired by one they’d seen at Marella Agnelli’s home in Corsica and reinterpreted in her home in Marrakech—one of the jewels in their enviable portfolio.

The two established their company, Studio KO, four years after they first met, and attribute their astonishing early success to the serendipitous choice of Morocco as the destination for their first summer holiday together. Fournier’s aunt has a house in Fez, and his father was born in Tunisia. “So there is something about Arabic culture in my family,” he explains of their choice at the time. They stayed in a small guesthouse in the Marrakech medina and planned an adventure that took them from the deserts of Morocco’s deep south to Mediterranean-breezed Tangier in the north. By the end of their odyssey, the country was in their blood.

On a subsequent trip they met their friend Pascale Mussard, a longtime artistic director at Hermès, who told them that her cousin Patrick Guerrand-Hermès was looking for young architects to work with on some projects that he was developing in the north of the country. Marty and Fournier ultimately spent a year on those Guerrand-Hermès commissions in the seaside towns of Asilah and Larache, and the buzz of the association began to attract new clients. The two designed private homes, restaurants (including the storied 1920s Grand Café de la Poste), and hotels that bucked the prevailing trend for ersatz arabesque fantasias. The designers instead harnessed local materials and skilled craftspeople to create buildings that are linear, austere, and powerfully beautiful. “Morocco at that time was a very small society, with very few architects or designers,” notes Marty. “It was like a big playground. You were given the opportunity and the money to do beautiful things.”

As aficionados of Marrakech, they were asked to help Agnelli navigate it on a visit she made to look for a holiday house of her own. Agnelli had heard that the couple was close to Guerrand-Hermès, whose famed garden she was keen to visit. Not only did she visit but, after some complex negotiations, she acquired the property and brought in Fournier and Marty as architects. In a nod to their youth, Agnelli’s friend and long-term collaborator Gae Aulenti monitored the project and proved an unforgiving but inspiring mentor. “She probably taught us more than six years of school,” says Marty, laughing, “about a certain ethic of how to work, and the process. She was an amazing character. She can see a flaw on a plan for a huge house within one second—she has an eye for that, which is really crazy.”

Some time later they were invited by Pierre Bergé to tour the Villa Oasis, the legendary house neighboring the Majorelle Garden, which he restored with Yves Saint Laurent. “It was very intense,” remembers Marty, who wrote a thank-you note praising not only the house but the pioneering example that he and Saint Laurent had set as a very public gay couple.

Bergé would later commission them to work on Majorelle’s original studio in his garden complex, and then an enchanting turn-of-the-century villa in the heart of Tangier’s hustle and bustle. The architects are currently in the throes of another Bergé collaboration—a spectacular 40,000-square-foot Yves Saint Laurent Museum, neighboring the Majorelle Garden, that will house a rotating collection of the couturier’s remarkable fashion archive as well as his enchanting works on paper (the majority of which are conserved at the Fondation Pierre Bergé–Yves Saint Laurent in Paris).

Studio KO now has residential and commercial projects as far afield as Los Angeles, Gabon, where they are building an eco hotel, and London, where they joined André Balazs’s team to create his see-and-be-seen hotel the Chiltern Firehouse. “They have an integrity and a sophistication that reminds me of [Christian] Liaigre,” notes Balazs, “with a range of interests that goes from architecture to fabrics.” Their work has also taken them back to their beloved Corsica. Here they have recently completed a villa on the island’s southern tip near Porto-Vecchio, a structure of local granite that appears like an ancient walled fortress growing out of the maquis. With its black terrazzo floors, and pocket doors that disappear into the thick walls in the balmy summers, “it’s very Corsican,” says Marty. “It echoes well the roughness,” adds Fournier, “the intensity of the Corsican landscape.”

In Paris the couple live in a converted industrial space in edgy Montreuil, and they are finishing work on a traditional adobe farmhouse half an hour’s drive—but a world away—from bustling Marrakech. “A friend of ours said that it’s not a house,” says Fournier, “it’s a place for meditation!” But it is difficult for these two talented designers to find peace, with the Saint Laurent museum in full swing and an expansive palace in Marrakech’s Palmeraie to keep them occupied.

Corsica, however, remains something of a haven: “It’s like a little retreat,” says Marty. “When you’re worried about something, you always think, Oh, I have my little room there . . . I can go.”